Exhumation History of the Intermontane Belt in the Southern Canadian Cordillera: Insights from Low-Temperature Thermochronology
Bibliographic record
Abstract
The Intermontane belt of the southern Canadian Cordillera is a low-relief, structurally complex region composed of accreted island arc terranes that host significant Mesozoic porphyry Cu ± Au-Mo-Ag deposits. In contrast to the adjacent Coast and Omineca belts—both characterized by rapid, deep exhumation—the Intermontane belt has experienced comparatively limited erosion, raising questions about its Cenozoic tectonic and exhumation history. This study applies low-temperature thermochronological techniques, including apatite fission track (AFT), zircon (U–Th)/He (ZHe), and apatite (U–Th)/He (AHe) analyses, to quantify exhumation across the Intermontane belt. Thermal history modeling, supported by a regional compilation of thermochronology data, provides a detailed reconstruction of post-Mesozoic cooling and exhumation patterns. Results reveal a multi-phase evolution: (1) Jurassic/Cretaceous to Paleogene thermal stability (>150–60 Ma); (2) Paleogene (66–23 Ma) spatially variable cooling driven by reactivation of inherited faults (Yalakom and Pasayten systems), Cordilleran extension and core complex formation, and limited erosion in areas protected by volcanic covers such as the Ootsa, Endako, and Kamloops Groups; and (3) Miocene (20–0 Ma) localized reactivation of earlier structures under transtension, producing a patchwork of cooling ages. Additional volcanic shielding from the Chilcotin Group and a semi-arid climate (<400 mm/yr annual precipitation) helped preserve pre-Cenozoic thermal signals. In contrast, adjacent belts experienced widespread Miocene cooling due to higher erosion rates and deeper crustal exhumation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".